This proposal for the fifth year of the Maryland ICMR 1970-1975 program is designed for an active and productive period of international medical research. A principal objective is to enable American Scientists to study international health problems that have an impact on the United States. At our Pakistan Medical Research Center, studies of the genetics of the Culex mosquito vectors of Japanese B encephalitis, and of the Anopheles vectors of urban malaria will continue towards the objective of practical application of control measures. In the coming fiscal year, the addition of an American mosquito ecologist will strengthen our ability to undertake field release experiments with the genetically manipulated mosquitoes, and thus adapt the accumulated genetic research knowledge to the practical control of the major diseases carried by these mosquitoes. Participation in our overseas program of young American biomedical scientists, under expert mentorship, continues to be regarded as important. Collaboration with our host Institute of Hygiene in Lahore, and with relevant departments of the Panjab University, is maintained although for reasons of expertise this has never played a prominent part in the program. More important is a developing association with the Pakistan Medical Research Council. A more restricted program is planned for the Maryland ICMR unit in Salvador (Bahia), Brazil, limited to studies of the immunopathology of schistosomiasis, and genetic manipulation of the mosquito vectors of filariasis. Plans are for this program to terminate late in 1975 when the IRAP research workers will have fulfilled their engagements.